1. Field of the Invention
The present invention generally relates to a drive force distribution system. More specifically, the present invention relates to a drive force distribution system for a four wheel independent drive vehicle equipped with a separate drive motor for each drive wheel of the four wheel drive vehicle.
2. Background Information
An example of a conventional drive force distribution system is disclosed in Japanese Laid-Open Patent Publication No. 10-295004. The drive force distribution system described in this publication is used for controlling a four wheel independent drive vehicle that is equipped with a separate drive motor for each drive wheel of the four wheel drive vehicle. With the drive force distribution system described in this publication, when only one wheel of four drive wheels is slipping, the output torque that would have been distributed to the slipping wheel, if it were not slipping, is distributed instead to the non-slipping wheel on the same side of the vehicle as the slipping wheel. For example, if the slipping wheel is on the right side of the vehicle, then the output torque from the slipping wheel is distributed to the other wheel on the right side. Similarly, when two wheels located on opposite sides of the vehicle are slipping, the output torque that would have been distributed to each slipping wheel, if it were not slipping, is distributed instead to the non-slipping wheel located on the same side of the vehicle as the slipping wheel. In this way, the change in yaw moment that occurs when the drive force is revised (i.e., the difference between the yaw moment that exists just before the revision and the yaw moment that exists just after the revision) is suppressed. The yaw moment is a moment oriented about the center of gravity of the vehicle that occurs due to the longitudinal acceleration of the vehicle and the drive forces of the wheels.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved drive force distribution system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.